Pearson symbol

The Pearson symbol is used to describe the structure of crystalline substances and thus to map a geometric arrangement of atoms , molecules and ions in solid substances on a short string. The symbol contains the abbreviations for the crystal system and the Bravais lattice , as well as an indication of the number of atoms belonging to a unit cell.

The Pearson symbol has the structure xY i. Where x is an abbreviation for the crystal system, Y is an abbreviation for the Bravais lattice and i is a single or multi-digit number and thus describes the number of atoms in the unit cell. Usually x and Y are written in italics, e.g. the Pearson symbol for solid copper is cF 4, for crystalline sodium chloride cF 8.

The Pearson symbol can also be used to describe allotropic modifications in chemical formulas or substance names. To do this, add the symbol in brackets directly behind the corresponding expression. Ferritic α- iron can be described as iron ( cI 2) and austenitic γ-iron as iron ( cF 4).

Abbreviation for the crystal system Abbreviation description a triclinic , since t stands for tetragonal, the symbol a of the obsolete synonym is used anorthically c cubic (cubic) H hexagonal m monoclinic O orthorhombic t tetragonal

Abbreviation for the Bravais grid Abbreviation description P primitive grid S. base-centered grid F. face-centered grid on all sides I. body-centered grid R. rhombohedral grid

literature

• Nomenclature of Inorganic Chemistry - IUPAC Recommendations 2005 (PDF, 4 MB) ; Sections 3.4, p. 48 ff. And 11.5, p. 241 f.